Aircrafts which can takeoff and land vertically with a rotating wing, like a helicopter, are typically made in a configuration with a horizontally rotating main rotor and a vertically rotating tail rotor coupled to a gearbox and powered by a jet turbine engine. The vertical tail rotor is necessary for compensating the moment exerted by the main rotor on the body of the aircraft. The tail rotor, the gearbox and the coupling of these occupy much weight that otherwise could be useful load or otherwise could entail an energy saving.
Aircrafts are known that do not need the tail rotor and the gearbox and the coupling shafts, but where the rotor blades are powered by tip mounted ramjet engines that utilise the high speed at the tip of a rotary wing. However, it has appeared that the ramjet configuration is very noisy and energy consuming and has the disadvantage that the ramjet engines produce a highly luminous ring from the exhaust. Another system avoiding the tail rotor is disclosed in U.S. Pat. No. 4,702,437, where the rotor has exit nozzles powered by air form electro motors in each of the rotor blades and where the rotor is connected to the fuselage through a yaw control system which can rotate the shaft of the rotor relatively to the fuselage.
Another system is disclosed in German patent application DE 2029733 disclosing a helicopter with rotor wings having gas exit nozzles for driving the rotor, where the necessary gas is provided by a compressor driven by shaft from an electrical motor.
Also, there are other configurations where a jet turbine mounted in the body of the aircraft produces compressed air conducted to nozzles at the tip of the rotary wing or to the central part of the rotor as disclosed in FR 1424495. However, this necessitates complicated technology and produces great losses.
Alternatively, as disclosed in U.S. Pat. No. 3,052,305 by Jones et al., a helicopter is disclosed with a gas turbine mounted concentrically on the rotor assembly and rotating therewith. The combustion gases from the engine are led out to the blade tips and ejected tangentially to cause rotation of the rotor. Another alternative is disclosed in U.S. Pat. No. 5,984,635 by Keller, where a helicopter has an upper hollow centre circular plenum in gaseous communication with a plurality of hollow rotor blades. Pressurized gas from two jet engines adjacent to the helicopter body is supplied to the blades and ejected tangentially at the tip of the blades.
An even further alternative is disclosed in British patent application GB 1 229 577 by Eyre, where a helicopter is provided with cylindrical blades having a gas exit substantially along the entire length of the blades. Gas is provided from two gas turbines in the rotor hub above the cabin of the helicopter. This system has the advantage of being light weight due to the lack of gearing and transmission shafts. However, this system suffers from the fact that these cylindrical blades—which are far from today's aerodynamic blade profiles—have not yet been practically proven as being safe during use.
All these prior art systems are specialised systems that have a lack of general versatility and scalability.
A further system is disclosed in French patent FR 1.424.495 by Galy disclosing a helicopter with a rotor in which the exhaust nozzles of the rotor are closer to the central axis than the inner ends of the wings. The exhaust nozzles are fed with gas from a jet turbine which is provided on the back of the aircraft and connected to the rotor through a piping system.
Hereby is achieved that the rotor system is a simplified system by having a clear division of a drive part, including the rotary structure and the turbine, and one or more rotor blades. A clear division of technology is provided so that the drive part and the rotor blades may be developed and produced separately. For the same drive part, different sized rotor blades or type of rotor blades may be provided and attached to the rotary structure of the drive part. Thus, the drive part is a universal solution for a versatile rotor construction that can be easily scaled, adapted and re-used in other configurations without amending the drive part and only by mounting rotor blades with appropriate dimensions. Actually, conventional prior art helicopter rotor blades may be mounted to the drive part according to the invention.
The drive part has a rotary structure which holds the proximal end of at least one rotor blade—rather a plurality of rotor blades—and which gives the rotational driving force to the rotor blades to achieve a lift of the aircraft by the blades. Preferably, the rotary structure is constructed such that it favours minimum drag both in rotation and in forward flight and does not add to the lift of the system, or at least does not add any substantial lifting force to the system. The distance from the rotational axis to proximal end of the rotor blade is much smaller than the distance from the rotational axis to the distal end of the rotor blades. For example, the radius for the rotating rotary structure is less than half or less than one third of the radius of the entire rotor. Thus, typically, also the area spanned by the rotating rotor blades is much larger than the area spanned by the rotating rotary structure. In addition, the speed of the distal end of the rotor blade is much higher than the speed of the rotary structure due to the larger distance from the rotation axis. Therefore, the lift of the rotor blades is the entire or at least main cause for the lifting force.
An alternative rotor system for an aircraft is disclosed in EP 1 832 511 disclosing a rotor which is magnetically coupled to an outer ring in order to avoid the rotating shaft normally employed in helicopters.